Comprehensive study on improving the sodium storage performance of low-defect biomass-derived carbon through S or N doping

As a promising alternative to graphite, biomass hard carbon has attracted widespread attention in sodium-ion batteries (SIBs). Heteroatom doping can overcome the inherent shortcomings of hard carbon materials, such as low reversible capacity and poor rate performance. Herein, in this paper, a simple and efficient one-step synthesis method is adopted to pyrolyze the mixture of jute fiber carbon with urea (JFCN) or sulfur powder (JFCS) from high to low carbonization temperatures, and determines that high-performance doping is only suitable for relatively low temperatures. Benefiting from the low-defect and ordered structure doped by proper S or N under these temperatures, initial Coulombic efficiency and electrochemical stability of hard carbon materials have been significantly improved. Meanwhile, S doping is a more effective way than N doping, the former shows an ultrahigh reversible capacity exceeding 410 mAh g-1 after 100 cycles at 0.1 A g-1 and a remarkable rate performance of 234.3 mAh g-1 at 2.0 A g-1. Impressively, JFCN exhibits greater rate performance in ether electrolytes, while JFCS shows better stability in ester electrolytes. This work provides a broad application prospect for hard carbon materials to achieve low cost and high capacity as practical SIBs.